When Belgium became independent in 1830, the Belgian public debt was about 3% of the debt of the United Netherlands, the rest was Dutch debt accumulated mostly in the period before the annexation of 1810. In fact, Belgium only exists because the Dutch State could not honor the obligations they took onto themselves in the Treaty of Aachen of 1818, "Le traîté des forteresses".
The Dutch were ruined during the revolutionary wars when they had to equip and re-equip all the French troops that passed trough Holland, by the loss of the banking trade with GB due to the shortage of bullion, and the Berlin decree of 1810 when immense stocks of contraband were seized and destroyed.
Best regards,
Bruno